This invention relates to metal nanostructures. Metal nanostructures are of utility in many applications, including catalysis and sensors. Many applications would benefit from nanostructures with a narrow and well-defined range of sizes and shapes of the nanoparticles.
A number of patents exist concerning metal nanoparticles.
Lee et al. (U.S. Pat. No. 6,572,673) reports a process for preparing metal nanoparticles by using anionic surfactant and suitable metal salts in the absence of adding reducing agent, such that under the reducing power of the anionic surfactant itself, the metal salts can be effectively reduced into metal nanoparticles having a uniform particle size.
Goldstein (U.S. Pat. No. 6,645,444) reports a process of reductive synthesis of a metal ion complex where the metal ion complex ligands following reaction serve to prevent agglomeration and impart solubility to the resulting metal nanocrystal. The resulting metallic nanocrystals preferably form kinetically stable solutions, in contrast to suspensions.
Oh et al. (U.S. Pat. No. 6,660,058) reports the preparation of nanoparticles of Ag and Ag alloyed with other elements such as Pt, Pd, Au, Al, Cd, and S in surfactant solutions. The surfactant molecules have the intrinsic property to adsorb into the interface which is formed between two different phases. The surfactant molecules adsorb into the surface of nuclei in solution. The adsorbed surfactant molecules from the solution prevent the coalescence of particles and control the rate of particle growth. The size of particles formed in solution can be controlled in nm scale by choosing the proper kind and/or concentration of surfactants.
Shirai et al. (Chem. Commun. (2000) p. 623-4) reports the formation of Pt nanosheets with thickness of 2-3 nm containing hexagonal holes that were formed between graphite layers by hydrogen reduction of platinum chloride-graphite intercalation compounds.
Zheng et al. (J. Crystal Growth vol. 260 (2002) p. 255-262) reports the formation of Au and Ag nanocrystals with novel dendritic structures in mixed cetyltrimethylammonium bromide and sodium dodecyl sulfate solutions. The dendrites consist of a long central backbone with projecting needles having parallel symmetry with respect to each other rather than randomly ramified secondary branches.
Kuang et al. (Adv. Mater. 15 (2003) p. 1747-1750) reports a hydrothermal process for preparing dendritic PbS in the presence of surfactant; the PbS dendrites consist of a long central backbone with projecting needles having parallel symmetry with respect to each other rather than randomly ramified secondary branches.
Ahmadi (Chem. Mater 8 (1996) p. 1161-1163) reports the formation of platinum nanoparticles with cubic shape in addition to previously reported tetrahedral, icosahedral, and cubooctahedral platinum particles. Nanodendrites are not formed by this method.